Diagnosing & Solving Water Hammer


If you’re annoyed by banging and hammering noises in your plumbing, you have a problem you want to fix as soon as possible, if only to save your sanity. Should you call the plumber immediately or is there something you can do to stop the noises on your own?

What Causes Noises in Plumbing?

There are two causes of noise in plumbing:

  1. Air hammer is a result of air being trapped in your water pipes. It happens when you turn on a faucet or valve.
  2. Water hammer happens when you suddenly shut off the water. It often starts with a big “bang” followed by a series of diminishing hammering sounds.

When you turn on a faucet or valve and air is trapped in a pocket or pockets somewhere in your pipes, the air is compressed. Turning on the valve releases the pressure and causes a loud hammering sound like the sound of the air pressure being released from an air gun.

Water hammer works a little differently. The reason why it occurs when you turn off the water is because the momentum of the water causes it to crash into the faucet valve, causing an initial hammering sound. Further down in the pipes, an air cavity and a vacuum is formed. This makes the water surge forward repeatedly until the air pressure gradually diminishes.

Diagnosing and Solving Water Hammer

You may be able to stop air hammer from occurring by turning off the water at the mains, draining all the water from your pipes and then turning the water on again. This may work on water hammer, too, but if it doesn’t, the only other way to prevent it from happening is to slowly turn off your faucet to prevent the sudden onrush of water against the valve.

Modern plumbing systems have air chambers installed to prevent water hammer from occurring. If your plumbing system has these air chambers, they may be clogged with mineral deposits. A plumber can clean them and you won’t have to remind everyone in the family to slowly close the tap or taps where water hammer occurs.

If you live in an older home, you have two choices. You can reduce your water pressure and see if that works or you can get quotes for installing an air chamber into your pipes. This is probably the best solution, because if left unchecked, water hammer can cause pipes to burst. As annoying as those banging sounds are, a broken pipe is a far bigger problem and more expensive to fix.

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